1. Field of the Invention
The present invention relates to a method for cooling and lubricating chiplessly shaped metals and the shaping means for the metals, particularly for cooling and lubricating the rolls and/or the rolled material, for example, in cold rolling of metal strips in a rolling mill stand, by supplying emulsifiers as necessary and emulsions which contain at least one oil phase. The invention further relates to an arrangement for carrying out the method.
2. Description of the Related Art
In chipless or non-cutting shaping of metals, the technological lubrication and cooling of the metals are becoming increasingly important in order to ensure that the increased requirements with respect to product quality during the production process can be met. In particular, an especially accurate maintaining of certain temperatures as well as an optimum surface geometry of rolls and rolled material are required during the shaping process of metal strip in rolling mill stands, so that a greater product quality of the rolled strip in cold rolling is ensured with respect to surface and planeness. The hydrodynamic separation of work surfaces of rolled bodies and strip surface also has an influence on the product quality. The requirements made of technological lubricants in cold rolling of fine sheet metal are generally met by emulsions having additives which are active during rolling. The effect of cooling, lubrication and force transmission in the roll gap is influenced by the rheological factors of the emulsions as well as by the addition of the emulsions when they are supplied to the roll gap. Thus, the design of the cooling and lubricating systems are of particular importance in planning and operating a cold rolling mill.
Emulsion circulating plans for cold rolling mills known in the art operate with several emulsion reservoirs, wherein the cold rolling emulsion generally is composed of a dispersion of oil in water with emulsifiers worked into the dispersion to ensure the stability of the emulsion. Each reservoir contains a cold rolling emulsion with a different emulsion characteristic. This makes it possible to supply the cold rolling mill with different cooling and lubricating media or cooling and lubricating concentrations.
Each rolling mill stand has a separate emulsion supply system composed of pump, filter and measuring and control system. The quantitative distribution of the emulsion over the width of the strip of the metal can be freely controlled by dividing the spray beams into nozzle zones. The emulsion is pumped back into the emulsion reservoirs from collection pits underneath the stands. Since each emulsion reservoir contains an emulsion with predetermined characteristic with respect to viscosity and density and with respect to cooling and lubricating properties as well as with respect to other parameters, such as, degree of dispersion, it is during the rolling operation only possible to utilize one of these predetermined emulsions. Moreover, the emulsion reservoirs must be sufficiently large because they simultaneously serve as sedimentation basins in which the preliminary cleaning of the emulsions is carried out. This means that large container constructions and complicated machines and plants of large size are required.
It has also been found that foreign contaminations can only be insufficiently removed from conventional cold rolling emulsions. Because of the foreign contamination, the emulsion is not a three-component mixture but a multicomponent mixture. The shaping process leads to metal abrasions and crack products from the oil phase. The inflow of foreign oil, for example, from leakages of the hydraulic systems, creates a multiphase mixture from which materials which negatively influence the lubricating possibility and the cleanliness of the strip can no longer be removed sufficiently and with sufficient accuracy.
It has further been found that the character and the lubricating capability of the emulsion is substantially influenced particularly by iron abrasion occurring during the shaping process which abrasion is almost exclusively adhesively bound to the oil phase. Experience has further shown that, due to insufficient sealing systems between the individual stands or in a multiple stand cold rolling mill, it is unavoidable that emulsion is carrier from one system into the next and, thus, cancel the different effects of the emulsions. The continuous circulation of a premixed emulsion also changes the inner structure and the lubricating capability of the emulsion.
European patent 0 054 172 describes a method for rolling tension-free rolled strip by influencing the coefficient of friction between the strip surfaces and the rolled surfaces. Depending on the strip tensions measured behind the rolling mill stand, in addition to the rolling oil emulsion sprayed onto the rolling gap, a basic rolling oil is applied to the surface of the rolled strip before the strip enters the rolling mill stand. The additional application of basic oil on the rolled strip made it possible to influence the planeness of the cold rolled strip.
However, it is only possible to meet today's great requirements with respect to product quality of cold rolled sheet metal and particularly the demands of rolling mill operators for a greater output of cold rolled steel strip in a cold rolling mill if the cooling and lubricating processes in the rolling gap or at the rolls can be influenced even more accurately and precisely than in the past. Thus, a greater quality of the product can only be ensured by a determined control/regulation of the frictions of coefficient in the gap between roll and rolled material and by means of an adjusted and deceleration-free changing of the properties of the emulsion which is supplied to the rolls.
In view of the above technological background, it is the primary object of the present invention to provide a novel cooling and lubricating system for cold rolling mills in which any desired oil concentration and any desired degree of dispersion in the emulsion can be adjusted at any time and with as little time delay as possible. It is to be made possible that the oils used are mixed in a predetermined manner with components which are active during rolling. In addition, an improved cleaning of the media collected behind the rolling mill is to be ensured by separately processing and cleaning the liquid phases which have been separated from the used emulsion. The size of the container structures and the machines required for cleaning and supplying the cooling and lubricating media are to be reduced and the use of emulsifiers which influence the environment is also to be reduced.